The metabolic and hormonal control of food and water intake in normal man and in patients having diabetes mellitus will be studied during experimental hunger and thirst induced by glucopenia and food deprivation. The central nervous system neurotransmitter control of food and water intake in normal and overweight man will be studied during experimental hunger and thirst induced by glucoprivation. Studies involving normal weight and obese subjects will help delineate the role of cognitive and/or metabolic factors controlling food intake. Prior to and following varying periods of caloric deprivation feeding patterns will be examined in lean and obese subjects utilizing an electronically activated feeding machine. Comparison of meal patterns will be made under similar conditions, where either liquid or solid diets are consumed. Lastly, feeding patterns will be examined during hyperphagia associated with uncontrolled diabetes. In addition the effect of insulin on meal patterns in diabetes will be observed.